<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>遇事问春风</title>
</head>
<style>
    .three>input:focus {
        color: red;
    }
</style>
<body>
    <div class="three">
        <input type="text">
        <input type="text">
        <input type="text">
        <input type="text">
    </div>
</body>
</html>